One technology of interest to the present invention is that found in Japanese Unexamined Patent Application Publication No. 2011-100998. This publication discloses, particularly in FIGS. 1 and 3, a package for an electric double-layer capacitor having a tray-shaped body and a lid.
Electric double-layer capacitors or similar electrical storage devices, which have a package accommodating positive and negative electrodes and electrolytic solution, should be improved to consume less of the electrolytic solution since the electrolytic solution is expensive.
The electrolytic solution must fill the space between the positive and negative electrodes so that ions can move between the pair of electrodes. This means that the electrical storage device can operate with no electrolytic solution in any part other than the space between the positive and negative electrodes; allowing the expensive electrolytic solution to exist is fairly meaningless unless between the two electrodes.
For this reason, the use of electrolytic solution in electrical storage devices should be minimized. However, packages designed as in the publication mentioned above are not effective in reducing the amount of use of the electrolytic solution because the electrolytic solution spreads and gets into some internal spaces which should be empty.